A multi-hop radio communication system has presently attracted attention. In the multi-hop radio communication system, a terminal apparatus performs radio communication with an access point through another terminal apparatus. If the terminal apparatus is incapable of direct radio communication with the access point, the terminal apparatus can transmit data to the access point through the other terminal apparatus. This enables an increase of a data arrival rate to the access point with a reduced delay. As examples of the multi-hop radio communication system, there are a BAN (Body Area Network) and sensor networks for monitoring a forest fire, intrusion of a suspicious person, etc.
In the multi-hop radio communication system, radio communication may be performed by a TDMA (Time Divisional Multiple Access) method in some cases. In the TDMA method, each terminal apparatus performs radio communication using a time slot allocated thereto. Typically, there is a communication method in a beacon mode provided in an IEEE 802.15.6 standard. According to the beacon mode communication method, the terminal apparatus performs radio communication on the basis of time slot information that is included in a beacon signal received from the access point, for example.
The terminal apparatus using the TDMA method shifts to an operating state (or active mode) at the time slot allocated to the self-terminal, to perform data transmission and reception. On the other hand, in other than the allocated time slot, the terminal apparatus shifts to a power saving state (or sleep mode) in which data transmission and reception are not performed. Power consumption in the terminal apparatus is reduced by means of such intermittent operation.
As a technique related to such a radio communication system, there is a technique as follows, for example.
Namely, there is a radio communication system in which a hub, on detecting a communication disconnection with a node 4, requests nodes 2, 3 to search for the node 4, and if the hub receives from the node 3 a discovery notification of the node 4, the hub allocates a relay band, so as to perform radio communication with the node 4 through the node 3.
It is said that according to the above technique, power consumption in the relay node can be reduced because a relay node that discovers the node 4 transmits notification information, whereas a relay node that fails to discover the node 4 does not transmit any notification information.
Further, there is also disclosed a multi-hop radio ad hoc network system, in which all terminals and a gateway in a network perform switchover operation between activation and sleep, in synchronization with an activation cycle, an activation phase and an activation period, to execute data transfer during the activation period, whereas perform minimal operation during the sleep period.
According to the above technique, it is said that low power consumption can be achieved because of achieving an efficient sleep mode.
Moreover, there is also a radio communication apparatus, in which, as attribute information of at least the self-station and neighboring stations that are directly communicable with the self-station, relay capability data indicative of whether each radio station is available as a relay station is retained in the radio station, so that a neighboring station, which is capable of relaying and selected on the basis of the relay capability data of the neighboring stations, is utilized as a relay station.
According to the above technique, it is said that the radio communication apparatus, which is available as a radio station constituting a multi-hop radio communication network and available as a relay station and capable of preferentially executing communication of the self-station, can be provided.